The operator of a vehicle, such as an automobile or truck, normally has adequate visibility for the safe operation of a vehicle. The operator's visibility is enhanced through the well-known use of rearview and side view mirrors. However, when a driver is maneuvering a vehicle into a parking slot he generally cannot see portion of the vehicle that may make a contact.
A current concern among auto consumers and insurers alike is potential cosmetic damage caused by a very low speed collisions. Most vehicles now use a molded panel as part of an integrated bumper assembly. Such bumpers are designed to absorb high-speed impact forces, but are generally too stiff to dissipate the force from the low speed collision on the order of 5 miles per hour. Resultant reaction forces reflected back from a damper might cause cosmetic damage to the bumper panels that require panel replacement.
To solve problems of this nature, vehicular collision avoidance systems have been developed and are now relatively common. Such systems include apparatus for measuring distance between a vehicle and an obstacle in the vehicle's path and apparatus for displaying that distance or at least alerting the operator of an impending collision. For example, U.S. Pat. No. 4,903,004 issued Feb. 20, 1990, and entitled “All-Weather Digital Distance Measuring and Signaling System” (incorporated by cross reference) describes a distance measuring and signaling system for a vehicle specifically intended for accurately measuring distances from obstructions. An array of transducer devices having independent sending and receiving capabilities are mounted on a support frame, such as a bumper. A pulsed signal emanating from a transistor amplifier circuit is timed as it is converted to an ultrasonic wave signal by each transducer device, and simultaneously emitted and received by the transducer devices, and is returned as a pulsed signal. This signal is returned after bouncing back from an obstruction, and the time of the return is converted into a distance value by digital converter circuitry. The digital converter circuitry in turn sends the signal to a digital display device.
U.S. Pat. No. 4,674,073 issued Jun. 16, 1987 and entitled “Reflective Object Detecting Apparatus” describes an apparatus wherein a plurality of ultrasonic transmitting elements and ultrasonic receiving elements are provided and are electrically switched in a sequential manner to allow the existence of an obstacle to be detected. The distance to the object and a particular region at which it is detected is displayed. The ultrasonic transmitting elements and the ultrasonic receiving elements are alternately disposed in a linear array.
Unfortunately, known systems of the type described above generally suffer from a number of problems including detection accuracy, ground detection errors and lack of target classification. For example, whether an object is a static target, an automobile or a pedestrian. Furthermore, known systems are warning systems providing an audible warning sound or visual display.